Because, unlike other companies, when you purchase the Xbox One version of the game, you are simultaneously purchasing the PC version of the game. They are advertising the product you will be buying and clearly stating exactly which platform the one shown on screen is for. How is that misleading?

Edit: I would also point out, that at no point does it say 'Xbox One', it simply states 'Xbox', which is a service (not a console) that operates across Xbox One and Windows 10 PC. At the end of the trailer, it even states 'Xbox' and then underneath 'Xbox One | Windows 10'.

The only other thing they could have done is plastered 'Captured on PC' across the top of the screen. Even then, I am sure people would find a reason to complain.

Exactly. You'd have to be pretty naive if you thought this wasn't deliberately misleading. A video of a 4K game on a XBox Youtube channel with the mention of PC hidden behind 'show more' and ending with an advert for the XB1s ...

Come on now.

Because it starts off with the Xbox logo, has the Xbox logo on screen all the time and ends with an Xbox ad, yet they used PC footage. It's misleading!

I think I've read that NMS used old, better footage in latest adverts, that's misleading. If a Vita crossplay game used gameplay footage from the PS4 version of the game to advertise the Vita, that would be misleading. 

I think we should now pick on Titanfall 2. This trailer is running on PC but Xbox and Playstation re-used the footage and posted on their respective channels. This is so misleading: https://www.youtube.com/watch?v=F6cp95Xf6uw

Or maybe we should just pick on GoW because it's an exclusive?

Let's be honest guys, companies want to showcase the best version of their game. They aren't going to make a separate trailer for every single platform just to appease people that say 'Well, this trailer has too many pixels to run on that device'.

As I said, Xbox is not a console, it's a service now. They are advertising the game for a service, not a console. If Playstation advertised a game for PS Now, my version of the game may look worse than yours due to internet connection and/or the device I am playing it on. Sony however, would of course demonstrate the game working on the best device with a flawless internet connection. That doesn't make it misleading because they are demonstrating the product I am purchasing. It's up to me what device I run it on.

I think it's just marketing and they do want to showcase their best footage but it is also something that gets called out on the interwebs when companies do it.  That's probably why you see those little sayings "footage captured from ______ or run in ingame engine on ______" or however they word it.

Rest assured if Sony shows their next big relase with 4k pc footage there will be instant threads and this one will be forgotten.

Exactly. Of course it's on the Xbox channel, as it makes use of countless features of the Xbox PC app.
Be it achievements, cross play, streaming, party chat or whatever, you need the Xbox PC app.

If the game is playable on PC at 4K, and the console version includes a PC version and that's what they state in the video then I have no issue with that. If the game is exclusive to a console and they advertise the game as 'here is console footage' which is actually PC footage, THAT is misleading and should be addressed. This thread however makes no sense to me if I am honest.

If MS was going with full disclosure they would have started the video with "the following footage was captured from a $1500+ Win10 PC", instead they did pretty much the bare minimum by putting it in the description.
That's certainly legal, but a tiny bit shady.

I don't think that this is misleading. They explained it in the description. If people don't read and will complain it's their own fault.